Method of interconnecting two sheets of deformable material



E. C. FRAZE Aug. 3, 1965 METHOD OF INTERCONNECTING TWO SHEETS 0F DEFORMABLE MATERIAL 4 Sheets-Sheet 1 Filed March 2, 1964 E. C. FRAZE Aug. 3, 1965 METHOD OF INTERCONNECTING TWO SHEETS OF DEFORMABLE MATERIAL 4 Sheets-Sheet 3 Filed March 2, 1964 3 M //n Z 1965 E. c. FRAZE 3,198,155

METHOD OF INTERCONNECTING TWO SHEETS 0F DEFORMABLE MATERIAL Filed March 2, 1964 4 Sheets-Sheet 4 1W1? R U inner transverse end wall.

the invention, both the die faces are of curved convex United States Patent 3 198 155 METHOD OF INTERDNlJECTHNG TWQ SEEETS 0F DEFGRMA'BLE MATERIAL Ermal C. Fraze, 355 W. Stroop Road, Dayton, Ohio Filed Mar. 2, 1964, Ser. No. 348,712 Claims. (CL 113--12l) This invention relates to containers having tear strips adapted to be manually removed for access to the contents of the containers, and more particularly pertains to the structure of the joint between a tab and a tear strip, the joint being of sufiicient strength to permit the tab to function as a lever for initiation severance of the tear strip.

It is common practice to attach a tab to a tear strip of a container by providing an aperture in the tab, forming a hollow rivet in the tear strip, inserting the hollow rivet into the aperture, and then expanding or heading the hollow rivet into overlapping engagement with the tab. It has been suggested, moreover, that instead of forming an aperture in the tab, the tab as well as the tear strip may be formed with a suitably dimensioned hollow rivet and the two hollow rivets may then be telescoped together and headed or expanded to anchor the tab to the tear strip.

This last construction is advantageous because the bond between two telescoped hollow rivets is more tenacious than the bond between an apertured tab and a hollow rivet. Another advantage is that the two telescoped hollow rivets reinforce each other.

The problem is to fabricate such a joint of telescoping rivet elements efficiently and economically without rupturing the metal wall of the container. The difiiculty is that the initial distortion of the sheet metal to form the two hollow rivets strains the two metal sheets to such extent that subsequently heading the telescoped hollow rivets by the usual procedure of axial compression is too drastic and causes the metal to crack and break.

If an attempt is made to expand or head the two telescoped hollow rivets simultaneously by squeezing the double layer end wall across its thickness dimension by conventional fiat faced dies, another difliculty arises in that the transverse end wall of the innermost telescoped hollow rivet is confined by the outer hollow rivet to interfere with radial expansion of the transverse end wall.

Upon investigation, it is found that the squeezing action thins both of the two transverse end walls with consequent radial expansion of the two end walls by extrusion, nevertheless, the radial expansion of the outer end wall is not adequate to prevent hinderence of radial expansion of the inner end wall.

The invention meets this difiiculty by using a convex outer die to exert the squeezing pressure against the outer transverse end wall of the double layer hollow rivet. It has been found that if the working face of the cooperating inner die that is inserted into the telescoped rivets to act on the inner transverse end wall is more nearly flat than the working face of the outer die, a differential radial flow occurs in which the metal of the outer transverse end wall extrudes radially further than the metal of the inner transverse end wall and, of equal importance, the radial extrusion of the outer transverse end wall is initiated in advance of the expansion of the In the preferred practice of configuration but the outer die face has the shorter radius of curvature to produce the desired effect.

The preferred practice of the invention is further characterized by first forming dimples of relatively large area in the two sheet metal parts and then transforming the dimples into the desired steep shouldered bosses or hollowrivets. The advantage of this procedure is that it crowds metal into the area of a hollow rivet and thus makes the walls of the hollow rivet thicker than would otherwise be possible. The increased thickness of the walls of the two telescoped hollow rivets provides more metal for the operation of radial extrusion of the two transverse end walls and, in addition, reduces the susceptibility of the hollow rivets to cracking.

T o achieve a highly effective joint it is essential that the two hollow rivets be dimensioned for snug telescoping lit and therefore the two bosses must be of accurate dimension relative to each other. Care is necessary to avoid, on the one hand, too loose fit by the two bosses and, on the other hand, such a tight fit as to make it difficult to telescope the two bosses together in preparation for the final heading operation.

A feature of one practice of the invention is the concept of placing the two sheet metal parts together face to face and applying dies to the double layer assembly to form both bosses or hollow rivets simultaneously in nested or telescoped relation. This procedure not only assures snugger fit between the two bosses than is otherwise possible but also eliminates the step of inserting one boss into the other and thus reduces the cost of fabrication.

The features and advantages of the invention may be understood from the following detailed description and the accompanying drawings.

In the drawings, which are to be regarded as merely illustrative:

FIG. 1 is a plan view of the metal end wall of the can showing a dimple formed therein in preparation for forming the desired hollow rivet;

FIG. 2 is a fragmentary section along the line 2-2 of FIG. 1 showing the cross-sectional configuration of the dimple and also showing how dies may be employed to form the dimple;

FIG. 3 is a view similar to FIG. 1 showing the hollow rivet that is produced for suitably transforming the dimple;

FIG. 4 is a fragmentary cross-section along the line 44 of FIG. 3 and also showing how dies may be used to transform the dimple into the hollow rivet;

FIG. 5 is a fragmentary sectional view on an enlarged scale showing a steep shouldered boss or hollow rivet formed in the metal wall of the can and further showing a similar steep shouldered boss or hollow rivet formed in a tab to telescope over the first boss or hollow rivet;

FIG. 6 is a greatly enlarged sectional view showing the two hollow rivets of FIG. 5 telescoped together and fur ther showing how a pair of dies may be positioned to head the hollow rivet by radial extrusion by the metal of the two transverse end walls of the telescoped hollow rivets;

FIG. 7 is a view similar to FIG. 6 showing the completion of the extrusion operation;

FIG. 8 is a plan view of the can top, the fabrication of which includes the steps illustrated by FIGS. 5, 6 and 7;

FIG. 9 is a sectional view along the angular line 99 of FIG. 8;

FIG. 10 is a greatly enlarged fragmentary cross-section showing how the scoring may be on the outer surface of the can top;

FIG. 11 is a similar view showing how the scoring may be on the inner side of the can top;

FIGS. 12 and 13 are sectional views showing how' a double layer hollow rivet projection outwardly of a can top may be formed by die means;

FIG. 14 is a sectional view illustrating the step of heading or expanding the double layer rivet;

FIGS. 15 and 16 are sectional views showing how die means may be formed to employ a double layer hollow rivet that projects inwardly of the can top; and

FIG. 17 is a sectional view illustrating the operation of expanding or heading the inwardly projecting double layer rivet.

vIn the first practice of the invention illustrated by FIGS. 7

1 to 7, hollow rivets are formed separately in a can top than the desired hollow rivet and then transforming the. J

dimple into the hollow rivet. Thereafter thetwo hollow rivets are telescoped together to form a double layer hollow rivet and the double layer hollow rivet is expanded or headed by squeezing the double layer transverse end wall of the hollow rivet to cause radial extrusion of the metal.

FIG. 1 shows a conventional sheetmetal'top for a can that is intended to contain a beverage, the can top being made of a suitable material such as aluminum or steel. A dimple 22 of generally conical configuration and of relatively large area is formed in the can top 20 and is subsequently transformed into a hollow rivet that is 4 placement'or extrusion'of the metal of the two end walls with consequentradial expansion of the two end-walls to a form a circumferential double layer bead 52 in the double layer hollow rivet. It is apparent that when the double .layer hollow rivet is expanded or headed in this manner,

the two sheets of metal are positively interlocked to form a joint capable'of withstanding high stresses.

I lt'is-to be noted that in the operation of heading the double layer hollow rivet the greater curvature of the upper die causes the'radialdisplacernent of the imetal of the outer transverse end wall 42 to occur promptly and to extend further than the radial displacement of the metal generally designated 24 inFIG. 3,. the hollow rivet being of substantially smaller area than the dimple.

FIG. 2 indicates the general manner in which the dimple 22 is formed. The can top 20 is placed between an upper annular die 25 and a lower male die 26, the upper die having a central cavity'28that is of substantially greater ly inwardly into the die cavity. In such a die operation the dimple is'formed with no'significant thinning of the sheet metal.

After the dimple is formed, the hollow rivet 24 is formed by die means of the general character shown in FIG. 4. The upper die 39 in FIG. 4 has a cavity 32 of the overall area of the desiredhollow rivet and of substantially greater depth than the height of the desired hollow rivet. The lower die 34 is formed with a projection 35 that is of the area and depth of the interior of the desired hollow rivet. with liberal tolerance in cross sectional area to minimize drawing action on the sheet metal and consequent thinning of the side walls of the hollow'rivet. When the two dies 30 and 34 close the metal of the area of the dimple 22 is crowded radially inwardly with a thickening effect on the walls of the hollow rivet 24, and by virtue of the depth of the upper die cavity 32 there is minimum thinning effect on the transverse .end wall 36 of the hollow'rivet,

A tab, generally designated 38 in FIG. 5,is processed in the same manner to form therein a hollowrivet, gen erally designated 4 with a transverse end wall 42, this second hollow rivet being dimensioned to telescope snugly over the first hollow rivet 24 in the can top 20'. FIG. 5 shows the two hollow rivets 24 and'40 aligned to telescope together and FIG. 6 shows the two hollow rivets telescoped together. i

FIG. 6 shows the two telescoped hollow rivets 24 and 4t positioned between an upper die 44 and a lower die 45 in preparation for the final heading operation. The, lower die has a projection 46 dimensioned to fully. occupy the interior of the inner hollow rivet 24 and thus support the double'layer hollow rivet from the interior to prevent axial compression of the hollow rivet. The upper die 44 which preferably serves as an impact member has a leading face 48 of arcuate convex configuration. vThe leading face 50 of the lower die 45 may be flat but preferably is also of arcuate convex configuration. The radius of, curvature of the upper die face 48 must be appreciably lessithan the radiusof curvature of the lower die face 50. As here-' tofore explained, .theshaper curvature of the leading face I of'the inner end wall 36. Thus the greater curvature of v the upper die 44 keeps the outer hollow rivet 44 from ferential" groove 54 and a curved peripheral-flange 55.

The tab 38 is formed with an upwardly inclined flange I 56 at its free end and'is further formedwith a central The upper cavity 32 is dimensioned longitudinal rib 58 and two longitudinal side ribs 69, the purpose of the ribs being to make the tab sufiiciently rigid for it. to function effectively as a second-class lever for initiating thelseverance of a tear strip 62 in which the inner hollow rivet 24, is formed; 7 The tear strip-62 is definedby a continuous "scored line 64 and the scoring may be on the outer surfaceof the can top as indicated in FIG; 10 or on'theinner surface. of the can top as indicated in FIG. 11. Usually it is desirable to score an aluminum can top from the outer side and to score a steel can top from the inner side. I

It is to be noted in PIG. 8 that the tab 38 is at an acute angle relative to the tear, strip 62 and it is to be further noted that thefulcrum end of the tab 38 is tapered to provide a. rearwardly inclined edge 65 that is at an acute angle relative to the longitudinal axis of the tab. When the free endof the tab is lifted to carry out the lever action, the tab fulcrums on the inclined edge 65 and is thereby guided in an arcuate path which defines a portion of a conethat is concentric to the fulcrum edge. The

. described arrangement is inherently conducive to a lever- 7 on both ofv the sheet metal parts simultaneously to produce the two hollow rivets simultaneously with the two hollow rivets nested or telescoped together.

FIG. 12 shows how a double layer assembly comprisingia can top Ztld and a tab 38a'ma'y'be' positioned between an upper die'70 and a lower die .72, which two dies are ofthe general character of the previously described dies 30 and 34. The upper die has a cavity 74 of greater depth than the height of the, desired double layer hollow rivet and is further; formed with a vent passage 75. The

1 lower. die 72 has a projection 76 dimensioned to fill the 48 of the upper die 44 produces a more pronounced radial cavityof the desired double layer hollow rivet.

v The twodies 70 and 72 are moved close together as shown in FIG. 13 toform the desired double layer hollow rivet, generally designated 78. Here again the cavity 74 is of ample cross sectional dimension to minimize the fdrawing action on theflside walls of the double layer hollowrivet. I I

FIG. 14v shows in a simplifiedmanner how the double layerhollow rivet-78. is expanded or headed by the cor- FlG. 7 shows how thetwo dies 44.and 45 are brought f close together to squeeze the two transverse end Walls 36 and 42 across their thickness. and thu's cause radial disporation of'an upper-dief80 with a lower die 82. The lower die 82 has a projection or boss 84 which fills the interior of the double layer hollow rivet in contact with the double layer transverse endwall to lgeep the double layer hollow rivet from being subjected to axial compression. In accord with the teaching of the invention the upper die 89 has a leading face 85 that is of sharper curvature than the leading face 86 of the lower die.

FIGS. 15 and 17 show how the same procedure illustrated by FIGS. 12 to 14 may be employed to form a double layer rivet that projects inwardly of the can top.

FIG. 15 shows a tab 38b imposed on a can top 2% and shows how an upper die 72 may cooperate with a lower die 70 to form the double layer hollow rivet 88 shown in FIG. 16. The upper die 72 in FIG. 15 is the same as the lower die 72 in FIG. 12 and the lower die 70 in FIG. 15 is the same as the upper die 70 in FIG. 12. FIG. 16 shows the hollow rivet completely formed and FIG. 17 shows how the hollow rivet may be headed or expanded in the previously described manner. In FIG. 17 the upper die 82 is the same as the lower die 82 in FIG. 14 and the lower die 80 in FIG. 17 is the same as the upper die 86 in FIG. 14.

My description in specific detail of the selected embodi- DIEIltS of the invention will suggest various changes,

substitutions and other departures from my disclosure within the spirit and scope of the appended claims.

I claim:

1. A method of interconnecting two sheets of deformable material, including the steps of:

forming two hollow rivets with transverse end walls in the two sheets respectively with one hollow rivet dimensioned to telescope into the other; telescoping the two hollow rivets together with the two transverse end walls of the rivets close together; telescoping a first die member into the telescoped hollow rivets to contact the inner of the two transverse end walls; and

without subjecting the tubular walls of the telescoped hollow rivets to axial compression, placing a second die member against the outer transverse end wall to cooperate with the first die member to squeeze the two transverse end walls simultaneously across their thickness to reduce the wall thicknesses and extrude the metal of the two transverse end walls radially to expand the two hollow rivets radially adjacent the two transverse end walls thereby to positively mechanically interlock the two hollow rivets.

2. A method as set forth in claim 1 in which the second die member has a leading face of curved convex configuration to expedite the radial displacement of the metal of the outer transverse end wall.

3. A method as set forth in claim 1 in which both of the die members have arcuately curved convex faces with the radius of curvature of the face of the second die member less than the radius of curvature of the face of the first die member to cause the metal of the outer transverse end wall to flow radially faster and further than the metal of the inner transverse end wall.

4. A method of interconnecting two sheets of deformable material, including the steps of:

forming dimples in the two sheets respectively;

forming the two dimples into corresponding hollow rivets with transverse end walls of substantially smaller area than the dimples with one hollow rivet dimensioned to telescope into the other; placing the two sheets together in face to face relationship with the two hollow rivets telescoped together;

telescoping a first die member into the telescoped hollow rivets to contact the inner of the two transverse end walls; and

without subjecting the tubular walls of the telescoped hollow rivets to axial compression, placing a second die member against the outer transverse end wall to cooperate with the first die member to squeeze the two transverse end walls simultaneously across their thickness to reduce the wall thicknesses and extrude the metal of the two transverse end walls radially to expand the two hollow rivets radially adjacent the 6 two transverse end walls to positively mechanically interlock the two hollow rivets. 5. A method as set forth in claim 4 in which the second die member has a leading face of curved convex configuration to expedite the radial displacement of the metal of the outer transverse end wall.

6. A method as set forth in claim 4 in which both of the die members have arcuately curved convex faces with the radius of curvature of the face of the second die member less than the radius of curvature of the face of the first die member to cause the metal of the outer transverse end wall to flow radially faster and further than the metal of the inner transverse end Wall.

7. A method of interconnecting two sheets of deformable material, including the steps of:

placing the two sheets together face to face to form a double layer assembly;

applying male die means to one face of the assembly and female die means to the other face to form the two layer assembly into a double layer hollowrivet with a double layer transverse end wall;

inserting a first die means into the double layer hollow rivet and engaging the same against the inner surface of the double layer transverse end wall; and

while holding the first die means in engagement with the inner surface of the double layer transverse end wall, applying a second die means to the outer surface of the double layer transverse end wall to cooperate with the first die means to squeeze the double layer transverse end wall across its thickness to reduce the wall thickness thereof and extrude the metal of the double layer transverse end wall radially to expand the double layer hollow rivet radially near its outer end thereby to positively interlock the two sheets.

8. A method as set forth in claim 7 in which the second die member has a leading face of curved convex configuration to expedite the radial displacement of the metal of the outer transverse end wall.

9. A method as set forth in claim 7 in which both of the die members have arcuately curved convex faces with the radius of curvature of the face of the second die member less than the radius of curvature of the face of the first die member to cause the metal of the outer transverse end wall to flow radially faster and further than the metal of the inner transverse end wall.

10. A method of attaching a sheet metal tab to a sheet metal wall of a container within the area of a tear strip confined by a scored line on the metal wall, characterized by the steps of:

placing the tab and the tear strip in face to face relationship with hollow rivets with transverse end walls formed in the tab and tear strip respectively and with the two hollow rivets telescoped together;

inserting a first die member into the inner hollow rivet into contact with the inner transverse end wall of the two telescoped hollow rivets; and

while holding said first die member in contact with the inner transverse end wall of the telescoped hollow rivets, placing a second die member against the outer surface of the outer transverse end wall of the two telescoped hollow rivets to cooperate with the first die member to squeeze the two end walls across their thickness to reduce the wall thicknesses and to extrude the metal of the two end walls radially to expand the two telescoped hollow rivets radially to positively mechanically interlock the two hollow rivets,

said second die member having a leading face that is convex to expedite the radial displacement of the metal of the outer transverse end wall.

11. A method as set forth in claim It) in which both of the two die members have arcuately curved convex leading faces, the radius of curvature of the leading face of the second die member being substantially less than the radius of curvature of the leading face of the first die is, w] r member to expedite the radial displacements of the metal of the outer transverse end wall.

12." In a method of interconnecting two sheets of deformable material wherein at an intermediate stage in the method, hollow rivets in the two sheets having transverse end walls are'telescoped together to form adouble layer hollow rivet with a double layer transverse end wall, the improvement for heading the double layer 1 hollow rivet for positively interlocking the two sheets comprising: a I V squeezing the double layer transverse end wallof'the double layer hollow rivet across its thickness without axially compressing the tubular Walls' of the double layer'hollow rivet thereby to reduce the end wall thicknesses and extrude both layers of the double layer transverse end wall radially with consequent radial expansion of the double'layer end wall toform a double layer head'on the double layer hollow rivet.

13. In a method of interconnecting'two-sheets of deformable material wherein atan intermediate stage in the method, hollow rivets in the two sheets having trans,- verse end walls are telescoped together to form a double end wall. 5 7

layer hollow rivet with a double layer transverse end wall, I f

the improvement -for heading the double layer hollow rivet for positively interlockingthe two sheets comprising: inserting a'first die member into the interior of the double layer hollow rivet into contact with the inner 7 surface of the double layer transverse end wall;

placing a second die member against the outer surface of the double layer transverse end wall; and

while maintaining the first die member in contact with V the inner surface of said double layer transverse end wall, narrowing the gap between the two die members to squeeze the double layer'transverse end wall across its thickness to reduce the thickness and V extrude both layers of the double layer transverse end wall radially with consequent radial expansion of the double layer hollow rivet adjacent the double layer transverse end :wall to positively mechanically interlock the two hollow rivets and, thereby interconnecting said two'sheets 14. An improvement as setforth in claim 13 inwhich both of. the two die members have arcuately curved convex leading faces, thevradius of curvature of the leading face of the second die member being substantially less than theradius of; curvatureof the leading face of the first die member toexpeditethe radial extrusion of the metalof the outer layer. of the double layer transverse 15. Animprovement as set forth in'claim 13 in which at least one ofthe tw-o die'members has an arcuately curved convex leading face.

References Cited by the Examiner UNITED, STATES P AT ENTS WHITMORE A. WILTZ, Primary Examiner. CHARLIE T. MOON, Examiner. 

1. A METHOD OF INTERCONNECTING TWO SHEETS OF DEFORMABLE MATERIAL, INCLUDING THE STEPS OF: FORMING TWO HOLLOW RIVETS WITH TRANSVERSE END WALLS IN THE TWO SHEETS RESPECTIVELY WITH ONE HOLLOW RIVET DIMENSIONED TO TELESCOPE INTO THE OTHER; TELESCOPING THE TWO HOLLOW RIVETS TOGETHER WITH THE TWO TRANSVERSE END WALLS OF THE RIVETS CLOSE TOGETHER; TELSCOPING A FIRST DIE MEMBER INTO THE TELESCOPED HOLLOW RIVETS TO CONTACT THE INNER OF THE TWO TRANSVERSE END WALLS; AND WITHOUT SUBJECTING THE TUBULAR WALLS OF THE TELESCOPED HOLLOW RIVETS TO AXIAL COMPRESSION, PLACING A SECOND DIE MEMBER AGAINST THE OUTER TRANSVERSE END WALL TO COOPERATE WITH THE FIRST DIE MEMBER TO SQUEEZE THE TWO TRANSVERSE END WALLS SIMULTANEOUSLY ACROSS THEIR THICKNESS TO REDUCE THE WALL THICKNESSES AND EXTRUDE THE METAL OF THE TWO TRANSVERSE END WALLS RADIALLY TO EXPAND THE TWO HOLLOW RIVETS RADIALLY ADJACENT THE TWO TRNSVERSE END WALLS THEREBY TO POSITIVELY MECHANICALLY INTERLOCK THE TWO HOLLOW RIVETS. 